Change in visually perceived eye level without change in perceived pitch

Area of Science:

• Visual perception
• Human spatial orientation
• Psychophysics

Background:

• The visually perceived eye level (VPEL) is influenced by the physical pitch of a visual field.
• The implicit-surface model (ISM) proposes that a mental representation of spatial coordinates determines VPEL.
• Previous research indicates VPEL is affected by visual field pitch even in minimal visual conditions.

Purpose of the Study:

• To test the implicit-surface model (ISM) by examining the relationship between visual field pitch and visually perceived eye level (VPEL).
• To investigate how a rolled-from-vertical, two-line configuration in darkness affects perceived pitch and VPEL elevation.

Main Methods:

• Three subjects viewed a two-line configuration in total darkness at various roll orientations and horizontal eccentricities.
• Perceived pitch was measured using a manual matching procedure.
• VPEL elevation was determined by psychophysically setting a visual target to appear at eye level.

Main Results:

• Perceived pitch did not significantly deviate from vertical, regardless of roll or eccentricity, contradicting the ISM.
• VPEL elevation systematically varied with the roll of the configuration at eccentric viewing positions.
• VPEL elevation remained unchanged when the two-line configuration was centered on the median plane.

Conclusions:

• The results contradict the implicit-surface model's predictions regarding VPEL.
• VPEL elevation is influenced by the roll of the visual field, particularly at eccentricities.
• The findings support previous interpretations that VPEL variation is related to the average of individual line contributions.